It is not April 1, but Toyota’s Scion brand still came in dead last  in J.D. Power’s Initial Quality Study (IQS), which measures the number of problems on vehicles after 30 days of ownership.  GM had two brands (GMC and Chevrolet) in the study’s top five; Chrysler had none in the top ten.

This is the first time in the study’s 27-year history that GM or Chevrolet have been in the top five, or that GM as a company has come in on top.

The most trouble free vehicle was the Lexus LS, which was freshly redesigned for 2013, with 59 problems per hundred vehicles; the best brand was Porsche, with 80. GM’s four brands averaged 98, making GM the only automaker with less than one problem per car.

Power redesigned the study for 2013, the first change since 2006, to include new features, and to switch from paper to online responses.  The 233-question survey included answers from 83,000 customers. Almost two-thirds of problems were related to design, rather than defects.

The Chrysler brand ended up just above Lincoln and the industry average, with 109 problems per 100 vehicles; Lincoln and the average were 113. Jeep was a bit below average and almost tied with Land Rover, at 118 problems — still ahead of Volkswagen, Mazda, and Subaru. Dodge had 130 problems, almost even with Ford’s 131 and Ram’s 132.

While BMW fared moderately well, just below the industry average and head of Jeep and Dodge, Mini did poorly, with 135 problems per hundred cars. Fiat came in second to dead last, with 154 problems, and was saved only by Scion at 161.

Chrysler had two entries in the various “top three” lists, with Chrysler Town & Country beating Honda and Toyota minivans, and Chrysler 300 coming in just below Hyundai Azera and large-car segment-leader Chevrolet Impala.

The study’s broad definition of “quality” to include annoyances may mislead some who expect it to focus solely on manufacturing defects and breakdowns. The 90-day range makes it good for fast feedback to automakers, but a poor indication of the overall quality of the vehicles; the 14-month study is a better indication of long-term reliability. Generally, luxury brands have tended to dominate the 90 day edition, due to their dealers’ superior vetting of cars before they are passed on to customers.